open the extension manager, uninstall any extensions that are listed, then reinstall them.

you should install the Deprecated server behaviors extension first, then start DW and Close it. Then install the WebAssist Extensions to the extension manager.

After the extensions are installed to the extension manager, open DW to start the WebAssist installer. If the webAssist Installer does not launch automatically, open a PHP page to trigger it. After the WebAssist installer completes the installation, restart DW.

It is an extension that is bundled with Dreamweaver CC to replace the server behaviors functionality that Adobe removed:http://www.webassist.com/tutorials/Server-behaviors-for-Dreamweaver-Creative-Cloud